Issue: 19-12 July 30, 2019

Is the bark peeling from a tree that shouldn’t shed its In This Issue bark? August is National Tree Check Month: Are YOUR trees safe Are there tunnels or unusual patterns under the bark? and secure? Is there sawdust on or under the tree? Perennials for Shady Gardens Is there sap oozing down the tree? Septoria Leaf Spot on Dogwood Does the sap have a bad odor? Fragrant Sumac Succumbs to Fusarium Wilt Do sticky drops fall on you when you stand under the tree? Zombie Tree Needs Close Friends to Survive You might have spotted lanternfly. Please report it right away! August is National Tree Check Month: Now what? Are YOUR trees safe and secure? If you answered YES to any of the questions above, there’s a (Cliff Sadof, [email protected]) & (Elizabeth Barnes, [email protected]) good chance something is wrong. To decide if and how you should treat or report the problem, you’ll need to have a tentative When was the last time you really looked at your trees? It’s all diagnosis. Luckily, there are many ways to get one! too easy to just enjoy their cool shade and the sound of their leaves, but if you don’t know what to look for you could miss Know the tree species? Use the Purdue Tree Doctor to get a deadly diseases or dastardly demons lurking in their leaves and diagnosis and a recommendation on whether treating or reporting branches. A quick check can help you stop a problem before it is needed. This app allows you to flip through photos of problem kills your tree or your local forest! plagued leaves, branches and trunks to help you rapidly identify the problem. If you have an invasive pest, it will guide you how to National Tree Check Month is the perfect time to make sure your report it. tree is in tip-top shape! Our checklist will help you spot early warning signs of native pests and pathogens and invasive pests Don’t know the tree species and still need help? Reach out like Asian longhorned beetle, spotted lanternfly, and sudden oak to local experts. We’re happy to help! death. You can stop invasive pests in their tracks by reporting Purdue Cooperative Extension Service them if you see them. (https://extension.purdue.edu/) can answer your questions Is your tree healthy and normal? or direct you to a local tree care professional with the right expertise. Start by making sure you know the type of tree you have. Is it a Contact an arborist who can give you an assessment of deciduous tree like an oak or maple? Or is it an evergreen that your tree and specific treatment recommendations like a spruce or a pine? Don’t worry about exactly what species it (https://www.treesaregood.org/findanarborist). is. It’s enough for you to have a general sense of what the tree should look like when it’s healthy. Confused but think something is TERRIBLY WRONG? Contact Purdue’s Exotic Forest Pest Educator, report online, or Check the leaves call 1-866-NOEXOTIC. Are the leaves yellow, red or brown? Are they spotted or discolored? Do the leaves look distorted or disfigured? Is there a sticky liquid on the leaves? Perennials for Shady Gardens Do the leaves appear wet, or give off a foul odor? (Rosie Lerner, [email protected]) Are leaves missing? Plants differ in their adaptability to different growing conditions. Are parts of the leaves chewed? Sunshine is one of the most significant factors. We often think of light as being either sunny or shady, but, in fact, there are many Check the trunk and branches “shades” of light in between. Your garden may experience light Are there holes or splits in the trunk or branches? shade, such as that filtered through an overhanging tree; dense

1 shade, such as that found in woodlands; or intermittent shade be wet because of poor drainage; the latter is a more difficult from an object, such as a building that blocks the sun for only a situation. It’s wise to address the drainage issue before planting. portion of the day. The following lists suggest a selection of plants for part to full Some sites vary in their light exposure, depending on the season. shade, but be sure to do the rest of your homework in matching Wooded areas usually have much more sunlight in winter and species to site conditions. Note that some entries appear under early spring when the trees are bare than in spring and summer both flowers and foliage lists. Entries denoted with (N) are when foliage blocks the light. considered native. Most horticultural plants perform best in full sun but may be able Perennial Flowers to tolerate semi-shady conditions. Trimming nearby trees and Aquilegia sp. (columbine) shrubs may help increase the light. Some plants may produce lots (N) some species of lush foliage in the shade but produce few or no flowers unless Astilbe x arendsii (astilbe) adequate sunlight is available. Thankfully, a number of plants thrive in the shade. Bergenia cordifolia (heartleaf bergenia, pigsqueak) Brunnera macrophylla (Siberian bugloss) Darmera peltata (umbrella plant) (N) California and Oregon Hosta sp. (hosta, plantain lily) Lobelia cardinalis (cardinal flower) (N) Lobelia siphilitica (blue cardinal flower) (N) Mertensia virginica (Virginia bluebells) (N)

Variegated Solomon’s seal is a well-behaved, shade-loving plant. Polemonium caeruleum (Jacob’s ladder) Polemonium reptans (creeping Jacob’s ladder) (N) Polygonatum odoratum ‘Variegatum’ (variegated Solomon’s seal) Primula sp. (primrose) (N) some species Pulmonaria saccharata (lungwort, Bethlehem sage) Pulsatilla vulgaris (pasqueflower) Rodgersia aesculifolia (Rodgersia)

Pasque flower performs well with morning sun and afternoon Sanguinaria canadensis (bloodroot) (N) shade. Thalictrum aquilegiifolium (meadow rue) Viola sp. (violets) (N) several species Perennials Grown Primarily for Foliage Asarum canadense (wild ginger) (N) Athyrium filix-femina (common lady fern) (N) Athyrium niponicum var. Pictum (Japanese painted fern) Brunnera macrophylla (Siberian bugloss) Bloodroot blooms in early spring and its low-growing foliage dies Darmera peltata (umbrella plant) down in midsummer. (N) California and Oregon Hakonechloa macra ‘Aureola’ (Japanese forest grass) You don’t have to live in the tropics to have a stunning foliage display in your shade garden. Midwest gardeners have a Hosta sp. (hosta, plantain lily) wonderful foliage palette that can fill in areas among other Matteuccia struthiopteris (ostrich fern) (N) perennials, or even star as the focal point. Some perennials have Osmundastrum cinnamomeum (cinnamon fern) (N) both attractive flowers and foliage, so they provide season-long interest. Polygonatum odoratum ‘Variegatum’ (variegated Solomon’s seal) Another important factor to consider is soil moisture and Polystichum sp. (Christmas and Holly ferns) drainage. Plants vary in their requirement/tolerance of drought, (N) some species wet feet and soil quality. Soils can be wet with good drainage or Pulmonaria saccharata (lungwort, Bethlehem sage)

2 Rodgersia aesculifolia (Rodgersia)

Septoria Leaf Spot on Dogwood (Megan Haas, [email protected]) Ornamental dogwoods are prone to several leaf spot diseases, but the fungus, Septoria, is commonly found in Indiana. It causes angular, brown lesions bordered by a purplish color on the leaf. Fragrant Sumac Succumbs to Fusarium The leaf spot symptoms are similar to dogwood anthracnose, Wilt however, Septoria does not infect the twigs or branches so it is a (Tom Creswell, [email protected]) much less damaging disease. Throughout summer, spots may become numerous enough to cause early leaf drop. While the disease does not cause serious harm to the plant in any given year, multiple years of heavy infection may weaken the plant, making it more susceptible to other diseases or winter injury.

Figure 1: Highway median planting of fragrant sumac Fragrant sumac (Rhus aromatica) is a low growing native shrub that is valued for its adaptability to many soil types, wet or dry conditions, easy care as a ground cover, and for preventing erosion on slopes. It is often found in highway medians (Fig. 1), in parks or as a foundation planting around commercial buildings. The common name arises from the fact that crushing the leaves produces a lemon-like scent. The most commonly planted form is the variety ‘Gro-low’ which has nice fall color and usually stays about 2 to 3 feet tall instead of the 3-5-foot height of the native type. Septoria leaf spot on ornamental dogwood. Septoria overwinters in dead leaf material left around the plant. Starting in 2010, the PPDL began receiving samples of dying Spores can spread through wind and rain. Symptoms tend to first fragrant sumac from several locations around the state, including appear after periods of warm and humid weather and will Hancock, Marion, Porter and Tippecanoe counties (Fig. 2, 3). In progress through the summer. In severe cases, leaves will yellow each sample the main symptom was a striking internal and fall from the plant. discoloration of vascular tissue in the stems and crowns (Fig. 4, 5, 6). The fungus Fusarium oxysporum was consistently isolated from stem and crown tissue with internal discoloration, confirming Fusarium wilt as the main cause for decline.

Pycnidia are visible in an infected area of a dogwood leaf. To reduce inoculum for the following year, dead leaves should be raked from under the plant and disposed of. Dogwoods may be treated preventatively with a fungicide, beginning at bud break. Refer to the table below for recommended fungicides. Reapplication may occur two to three more times at 14-day intervals if conditions are favorable for disease development. Please follow all instructions listed on the fungicide label. Figure 2 Fragrant sumac being killed by Fusarium wilt

3 infested soil and the planting bed can easily become infested again from neighboring areas. The main recommendations in this situation are to plant a different type of shrub in the affected area and to avoid moving soil from this area to other areas with sumac. Clean shovels, other tools and boots by removing all soil with a wire brush before leaving the contaminated site then scrub tools with soap and water before using them elsewhere. The Fusarium strain present is unlikely to attack other types of plants so replanting with other shrubs/ground covers should be Figure 3 Fragrant sumac being killed by Fusarium wilt okay. Shrubs such as deutzia, landscape roses, juniper, nine-bark (modern powdery mildew resistant types) or spirea are just some The fungus responsible for the damage lives in the soil and infects of the potential replacements. through roots when a susceptible plant is present. Fragrant sumac (Rhus aromatica) and skunkbrush sumac (R. trilobata) are highly susceptible to this strain of the fungus. Smooth sumac (R. glabra) is not likely to be susceptible, however Fusarium wilt has also Zombie Tree Needs Close Friends to been reported on staghorn sumac (R. typhina). Survive (Kyle Daniel, [email protected]) Let’s get this out of the way….Plants and their ecosystems are amazing. To survive in so many environments with abundant or minimal resources without capabilities to migrate, plants are one of the most amazing organisms on the planet. Though research is abundant in above ground plant systems, below ground ecology is starting to show the vital importance that mycorrhizae, root grafts, and microbial action play in the health of individual plant and the surrounding ecosystems. Figure 4: Fragrant sumac stem showing discoloration of water conducting vessels just below the bark.

Figure 5: The same stem shown in Fig. 4 with bark removed to reveal dark brown to black sapwood discoloration typical of Fusarium wilt.

Figure 6: Crown tissue showing dark brown to black sapwood discoloration typical of Fusarium wilt.

Fungicides are not effective in this situation since the fungus resides in the soil and cannot be effectively eliminated. With this type of soil-borne disease we often get asked whether one may get rid of the problem by removing and replacing soil. Practical experience suggests it is nearly impossible to remove all traces of 4 Figure 1. Living, Leafless Stump of the Southern Conifer Agathis autralis (Kauri). Frontal view of the tree trunk remnant from the forest track (A). Oblique lateral view showing the typical gray- brown kauri bark with distinctive hammer mark pattern and decaying wood behind it (arrow) indicating the original trunk perimeter (dashed line) (B). Rear view showing a thick callus lining along the edge (arrows). The dashed line indicates the Figure 2. During daytime when host trees transpire vigorously, approximate original trunk perimeter (C). Source: Bader and the host tree profits from a larger root system and the stem water Leuzinger, Hydraulic Coupling of a Leafless Kauri Tree Remnant to potential (Ψ) is low (H). During nighttime and periods of low Conspecific Hosts, iScience(2019), evaporative demand, the living stump circulates water through its https://doi.org/10.1016/j.isci.2019.05.009 living tissues at Ψ close to zero. In the absence of transpiration,

A new research study found that a ‘dead’ stump, with no way for this water movement is likely driven by root pressure or osmolyte photosynthesis (i.e. leaves), was actually found to have a live and accumulation (I). Source: Bader and Leuzinger, Hydraulic Coupling functioning vascular system (xylem and phloem). Yes, you read of a Leafless Kauri Tree Remnant to Conspecific Hosts, that correctly, but how in the world is this possible? The study iScience(2019), https://doi.org/10.1016/j.isci.2019.05.009 found that sap flow is directly related to the surrounding tree, which indicates that mycorrhizae and/or natural root grafting via The sensor data found that during the day, when the live tree is the underground ecosystem flows through the stump into the photosynthesizing (thus needing more water), the water pressure tree. The most probable benefit of this strange relationship is the is low in the trunk while high in the tree. During the night, when root grafts/mycorrhizae is connected throughout the forests. This can help during drought to allow the surrounding trees to better little water is required by the tree, sap flows back into the trunk. survive drought conditions. Figure 2 shows the benefits for the The interconnected nature of underground systems is evident in tree and the stump. this study (Fig. 3).

5 Though there are limitations to this study as primarily there is only one stump and tree, so no replications can be developed, this information reinforces the need for more soil ecology understanding. With more replicated research, we can start to develop best management practices in improving soil ecology in ornamental plantings.

The Purdue Department of Horticulture and Landscape Architecture is fortunate to have one of the world’s leading microbial ecology leaders in our department. Dr. Lori Hoagland is developing data that is demonstrating the importance of considering soil ecology that we haven’t even considered in the past. You can find Dr. Lori Hoagland’s Soil Microbial Ecology Lab at this site: https://www.purdue.edu/hla/sites/hoaglandlab/

This is just a brief synopsis to this study. To read more about this publication (which is highly suggested), click this link: https://www.sciencedirect.com/science/article/pii/S258900421930 1464?via%3Dihub

Figure 3. Sap flow between the host tree and the living trunk during various times within a 24 hour period. This symbiotic Source: Source: Bader and Leuzinger, Hydraulic Coupling of a relationship is shown via arrows demonstrating the flow direction Leafless Kauri Tree Remnant to Conspecific Hosts, iScience(2019), of the water. https://doi.org/10.1016/j.isci.2019.05.009

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Purdue Landscape Report © Purdue University - www.purduelandscapereport.org Editor: Kyle Daniel | Department of Horticulture and Landscape Architecture, 625 Agriculture Mall Dr., West Lafayette, IN 47907

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